You will see commands ranging from 1-12. These are your custom command aliases. Select one that is not in use. Lets say command_1

Then type in the command that you want ran.

No on the left side of gconf go to global_keybindings.

Find the corresponding runcommand and double click.

In the value you will type in your shortcut for example, S

Now for this example Ctrl+Alt+s will open up the gnome-system-monitor.

Just repeat the steps to add more shortcuts. Just remember to try out the shortcut before you override it. You probably don’t want to assign a shortcut to something that is already used for something more important.

There are also some preset shortcuts you can set in System > Preferences > Keyboard Shortcuts.